The present invention relates to a process for the preparation of rubber laminates. More particularly, the present invention relates to a process for the preparation of rubber laminates, which comprises contacting a fluororubber containing specific compounding additives with an epichlorohydrin rubber, and bonding them by curing.
Recently, an increasing importance is attached to the resistance to alcohol-mixed gasoline and sour gasoline as the characteristics required of fuel hoses.
A fluororubber is excellent in the resistance to heat, oil, solvent and chemicals, and is used as a rubber excellent in the resistance to alcohol-mixed gasoline and sour gasoline.
Although the fluororubber has these excellent properties, it is more expensive that other rubbery materials such as an acrylonitrile/butadiene rubber and an epichlorohydrin rubber and is defective in that the cold resistance is poor.
Accordingly, a material formed by laminating a layer of a fluororubber composition having the above-mentioned excellent characteristics on a layer of an ordinary rubber composition attracts attention. However, the fluororubber can not be bonded by curing to an epichlorohydrin rubber according to customary procedures, or the bonding force is very weak. Therefore, any laminate having a high bonding strength has not been obtained.
As the means for improving the curing bonding force to a fluororubber, there have been proposed a process in which calcium oxide, an epoxy compound, an aldehydeamine or a 1,8-diazabicyclo[5,4,0]undecene salt of a carboxylic acid is incorporated in an epichlorohydrin rubber and the rubber is tightly cure-bonded to the fluororubber (see Japanese Patent Publication No. 61-29619), a process in which a 1,8-diazobicyclo[5,4,0]undecene salt of a carboxylic acid is incorporated in an epichlorohydrin rubber and/or a fluororubber (see Japanese Patent Publication No. 60-33663), a process in which a blend of a fluororubber with a small amount of NBR is cure-bonded to an epichlorohydrin rubber (see Japanese Patent Publication No. 60-6238), a process in which red lead and 2-mercaptoimidazoline are added to an epichlorohydrin rubber, to which at least one compound selected from the group consisting of calcium oxide, calcium hydroxide, magnesium oxide and magnesium hydroxide is further added, and the epichlorohydrin rubber composition is cure-bonded to a fluororubber or in which red lead, 2-mercaptoimidazoline and hexamethylenediamine carbamate are incorporated in an epichlorohydrin rubber, to which at least one compound selected from the above-mentioned group is further added, and the epichlorohydrin rubber composition is cure-bonded to a fluororubber (see Japanese Patent Publication No. 59-35787), a process in which a common curing system is incorporated in an epichlorohydrin rubber and a fluororubber (see Japanese Patent Publication No. 59-38896), and a process in which calcium hydroxide and a fluorinated surface active agent are incorporated in an epichlorohydrin rubber and the epichlorohydrin rubber composition is cure-bonded to a fluororubber (see Japanese Patent Application Kokai Publication No. 61-101553).
According to these processes, however, it is impossible to bond a fluororubber firmly to an epichlorohydrin rubber by curing, or the properties of the formed laminate are adversely influenced.